What is the projection theorem, what is the formula of the projection theorem

1. Projection theorem is also called "Euclidean theorem". In a right triangle, the height on the hypotenuse is the middle term of the ratio of the projection of the two right-angled sides on the hypotenuse. Each right-angled side is is the median of the ratio between the projection of this right-angled side on the hypotenuse and the hypotenuse.

2. Projection theorem is an important theorem in mathematical graphics calculation.

3. In Rt△ABC, ∠ABC=90°, BD is the height on the hypotenuse AC, then the projection theorem is as follows: BD2=AD·CD, AB2=AC·AD, BC2= CD·AC.

4. Proposed by Euclid, the famous ancient Greek mathematician and author of "Elements of Geometry".